device2yaml: add --newline option for quirky CLIs

[Vantomas]

Pre-Request Checklist

• Passes rubocop code analysis (try rubocop --auto-correct)
• Tests added or adapted (try rake test)
• Changes are reflected in the documentation
• User-visible changes appended to CHANGELOG.md

Description

extra/device2yaml.rb appends \n to every command it sends. Some quirky device CLIs (e.g. TP-Link) execute a command only on a \r\n, so with \n the commands are echoed but never run, and the captured simulation contains only the echoed commands with no output. There was no way to change this from the command line and each_line(chomp: true) strips a \r placed before the \n, so it can't be smuggled in via -c/-i.

This adds a -n/--newline option to control the line terminator:

• Default stays "\n" (no behaviour change).
• Accepts the \r, \n and \t escapes, e.g. -n '\r\n'.

Documented in docs/DeviceSimulation.md.

Example

bundle exec extra/device2yaml.rb user@host -n '\r\n' -c "show running-config"